AK4648 Datasheet, PDF (82/119 Pages) Asahi Kasei Microsystems – Stereo CODEC with MIC/HP/SPK-AMP

[AK4648]
2. READ Operations
Set the R/W bit = “1” for the READ operation of the AK4648. After transmission of data, the master can read the next
address’s data by generating an acknowledge instead of terminating the write cycle after receiving the first data word.
After receiving each data packet the internal 6-bit address counter is incremented, and the next data is automatically taken
into the next address. If the address exceeds 27H prior to generating a stop condition, the address counter will “roll over”
to 00H and the data of 00H will be read out.
The AK4648 supports two basic read operations: CURRENT ADDRESS READ and RANDOM ADDRESS READ.
2-1. CURRENT ADDRESS READ
The AK4648 contains an internal address counter that maintains the address of the last word accessed, incremented by
one. Therefore, if the last access (either a read or write) were to address n, the next CURRENT READ operation would
access data from the address n+1. After receiving the slave address with R/W bit set to “1”, the AK4648 generates an
acknowledge, transmits 1-byte of data to the address set by the internal address counter and increments the internal
address counter by 1. If the master does not generate an acknowledge but instead generates a stop condition, the AK4648
ceases transmission.
S
T
A
R/W="1"
R
T
SDA
Slave
S _Address
A
C
K
Data(n)
Data(n+1)
Data(n+2)
MA
MA
MA
AC
AC
AC
S
T
K
S
T
K
S
T
K
E
E
E
R
R
R
Figure 64. CURRENT ADDRESS READ
S
T
O
P
Data(n+x)
P
MA
MN
AC
AA
S
T
K
E
S
T
E
C
K
R
R
2-2. RANDOM ADDRESS READ
The random read operation allows the master to access any memory location at random. Prior to issuing the slave address
with the R/W bit set to “1”, the master must first perform a “dummy” write operation. The master issues a start request, a
slave address (R/W bit = “0”) and then the register address to read. After the register address is acknowledged, the master
immediately reissues the start request and the slave address with the R/W bit set to “1”. The AK4648 then generates an
acknowledge, 1 byte of data and increments the internal address counter by 1. If the master does not generate an
acknowledge to the data but instead generates a stop condition, the AK4648 ceases transmission.
S
T
A
R/W="0"
R
T
S
T
A
R/W="1"
R
T
SDA
Slave
S _Address
Sub
Address(n)
Slave
S _Address
Data(n)
Data(n+1)
A
A
A
MA
MA
C
C
C
AC
AC
K
K
K
S
T
K
S
T
K
E
E
R
R
Figure 65. RANDOM ADDRESS READ
S
T
O
P
Data(n+x)
P
MA
MN
AC
AA
S
T
K
S
T
C
E
EK
R
R
MS0625-E-01
- 82 -
2007/06